Die casting has been performed industrially for decades to produce high quality metal and metal alloy pieces that range from simple to complex in design at very at rapid rates. One industry relying on die casting as a significant portion of their manufacturing plants is the automotive industry. The metal pieces, i.e., wheels and engine blocks, produced therefrom are high quality, i.e., are dimensionally accurate with a very small margin of error and smooth. In order to produce the cast metal at high rates, hydraulic systems are utilized to inject the molten metal into the die chamber and to eject the cast metal from the die. Hydraulic fluids are not only the power source of the hydraulic system, but they have other functions in the system such as aiding in heat transfer, as a sealing agent, lubricant, among others. Typically, a die release fluid is sprayed onto the die to ensure that the cast metal is easily ejected from the die, i.e., molten metal does not stick to the die, and to ensure that the die cools between castings.
Unfortunately, die casting is not a closed process. Not only does hydraulic fluid leak from the hydraulic systems, but it is difficult to control the spray of die release fluid. It is not uncommon during operation for the die release fluid to coat the outside of the equipment and run down the equipment. Were it not for catch basins typically located beneath the casting equipment, the hydraulic fluid and die release fluid would pool on the ground, seep into the ground, or flow into ground drains.
Not only is this casting system messy and inefficient, i.e., both hydraulic fluid and die release fluid are wasted, but die casting is very expensive to perform due to the costs of the equipment, e.g., casting equipment, including the hydraulic portions, and dies. Adding to the high costs associated with die casting metals is the treatment and disposal of the waste generated during the casting process.
Due to the large amount of hydraulic fluid and die release fluid collected in the catch basins, others have attempted to separate water-soluble hydraulic fluid and water-soluble die release fluid for possible reuse or waste disposal using techniques such as membrane fluid separations. However, these attempts have failed, resulting in waste treatment of the hydraulic fluid and die release fluid. Treatment typically entails mixing the waste with water, thereby generating up to 100,000 gallons of waste water per day.
Although the industry recognized the significant expenses required for disposal of this amount of waste water, the industry has to date demonstrated no methods for altering the die casting process or reagent, reducing the amount of waste or more inexpensively disposing of the waste generated from die casting processes.